Capacitative coupling device



June 13, 1950 B. ADLER 2,5l1,524

CAPACITATIVE COUPLING DEVICE Filed April 6, 1949 'NVENTOR ezy'ma'n,Adler @M Mgg@ atented `une UNITED STATES PATENT OFFICE 2,511,524cAPACrrA'rIvii` COUPLIG nevica' Benjamn Adler, White Plains, N; Y.'Application April 6, 1949, Serial No. 851737 17 Claims. l

This invention relates to coupling devices more particularly of the typeincluding a capacitative pick-up member for transferring radio frequencyenergy from along the length of a coaxial cable transmission line to aradio frequency receiver.

Where a coaxial cable transmission line is tapped at various placesalong the length thereof to transfer energy from the line to radiofrequency receivers such as, for example, television receivers, if thetap should cause any change in the spacings of the conductors, as thevalue of the characteristic impedance of the line at the tap wouldchange, this would cause an impedance discontinuity in the line. Suchimpedance discontinuity would cause reflection of the signals passingalong the line with resultant standing waves and consequent loss ofenergy and distortion of the signal.

This loss of energy may cause such a weak signal to be transferred tothe radio frequency receiver that the signal to noise ratio would bevery low with resultant unsatisfactory functioning of the receiver.Moreover such defect Would be aggravated Where several receivers aretapped in along the length of the line, for due to the plurality ofimpedance discontinuities, successive receivers would receive less andless energy with the result that they would function in anunsatisfactory manner or not at all.

With these fundamental concepts of transmission line theory in mind, itis to be noted that Where a direct connection is to be made to theconductors of the coaxial cable along the length thereof, it isnecessary that a portion of the outer insulating casing rst be removed,the outer conductor severed and pushed apart to aord access to thedielectric casing in which the inner conductor is embedded, and suchdielectric casing must then be cut away so that a lead may be solderedor otherwise affixed to the exposed inner conductor.

After this is done, the dielectric casing and outer conductor must berestored so that they have substantially their original physicalcharacteristics, for as the coaxial cable is symmetrical along itsentire length, if the thickness of the dielectric casing is changed, asby melting because of the heat evolved during the soldering operation,or if the soldering should increase the diameter of the inner conductorat the joint, the spacing between the conductors would be changed and animpedance discontinuity would result with the attendant disadvantagesheretofore pointed out.

When conventional T-couplings are used to tap into the coaxial cable,the latter must be coinpletely severed, and precise soldering must bedone, without undue heating of the dielectricV casing, to aflix theindividual conventional coaxial connector required at each end of thesevered cable in order to join them to the T- coupling. The solderingoperations are relatively delicate to perform and time consuming andwould require the services of a skilled radio technician and at best thecoupling may still cause an impedance discontinuity in the line with theresultant reflections and standing waves on the line heretofore pointedout.

It is accordingly among the objects of the invention to provide a deviceof the above typeY impedance discontinuity in the line at the point oftransfer and consequent minimum amount of reiiection and standing waveson the line and hence a minimum loss of energy.

Another object is to provide a device of the above type that is simplein structure and relatively inexpensive to manufacture, having but fewparts which are sturdy and not likely to become out of order and for itsintended time.

According to the invention from its broader aspects, the transfer of thesignal voltage from along the length of the coaxial transmission line tothe radio frequency receiver is accomplished by means of a couplingdevice including a pickup member, placed against the dielectric casingof a section of the line from which the outer inwhich may be assembledpurpose in a relatively short sulating covering has been removed and theouter conductor severed to expose such dielectric casing, to form anelectric capacitor with respect to the inner conductor of the line.

The capacitative be in the form of a shell, desirably has an innerdiameter substantially the same as that of the outer conductor so thatit will snugly encomv1 pass the dielectric casing `and be flushtherewith. In order to close the break in the outer conductor and toprovide electrical continuity therepick-up member, which may 1y of, aconductive structure is provided having a portion thereof extendingparallel to the shell and spaced therefrom, means being provided on saidstructure to connect the severed ends of the outer conductor thereto.The structure is of such dimensions and so constructed and arranged thatthe pick-up member and said parallel portion will constitute a sectionof transmission line having a characteristic impedance substantiallyequal to that of the coaxial cable transmission line, thereby avoidingany 'substantial impedance discontinuity in the line due to theinterposition of the coupling device.

More specifically, according to one` aspect of the invention, theconductive structure may comprise a pair of substantially identicaltrays, each V having a semi-cylindrical floor thereinf'which floors whenthe trays are juxtaposed,Y form a' cylindrical cavity, and means aredesirably provided at each end of the trays and in communi; cation withthe floors thereof, to which, when suchftrays 'are' juxtaposed, thesevered ends of the outer conductor may be afxed and through which'thedielectric casing may extend.

'The c'apacitative pick-up member associatedv with said conductivestructure may comprise a pair of` semi-cylindrical shells affixedrespectively on the floors of said trays and each desirably slightlyless than a semi-circle in cross section so thatthe longitudinal edgesof the shells may be' 'slightlyf spacedfrom each other when the traysVare juxtaposed with said shells clamped againstsaid dielectric casing.

In the accompanying drawings in which are shown one' or'm'ore of variouspossible embodiments of the several features of the invention,

Fig. 1 is Van exploded perspective view of the device and the coaxialcable with the latter pre-r pared for mounting of said device,

Fig. 2 isa longitudinal cross sectional view of Y the device'mounted onthe coaxial cable,

YFig'. 3 is a diagrammatic View showing a receiver connected to thedevice, and

--Figl 4' is an equivalent circuit showing the device mounted on atransmission line and a receiver connected thereto.

Referring now to the drawings, the coupling device comprises acapacitive pick-up member I I and a conductive structure I2 in whichrsaid member may be positionedl The pick-up member desirably comprisestwo substantially semi-cylindrical shells or plates 2| and 22 of'conductive material having a radius of curvature substantially the sameas that of the dielectric casing I3 so that the latter may be interposedbetween such shells. Each shell desirably Nis slightly less thanV asemi-circle in cross` section so that a narrow gap 23 may be providedbetween 'each of the Ylongitudinal edges 24, 24' of the' shells whenthey are positioned around dielectrlccasing |3.

ln Vorder to retain the shells 2|, 22 snugly against said dielectriccasing I3, the conductive structure I2 desirably comprises two identicaltrays 25, 2t, which may be cast or otherwise formed from any suitablemetal.

Although Vthe shape of the exterior of the trays drical cavity 32 Iwillbe formed, dowel means 33 being provided to insure accurate alignment ofsaid floors 28.

Each of the trays desirably has a plurality of insulating grommets 38,illustratively two in number, extending through the base 39 of the trayand securely affixed in said base.

Although any suitable means could be used to affix the shells 2|, 22 totheir associated pair of grommets 33, in the embodiment herein shown, aplurality of spring spacerse!! are provided, illustratively two innumber, for each of said shells. lach spacer 40 desirably comprises areversely bent strip lof resilient conductive material having one of thelegs 4| thereof affixed as by soldering or welding to the convex surfaceof the associated shell. The other or outer leg 42 of the spacerdesirablyhas a threaded stud 43 aiiixed thereon, extending outwardlytherefrom, at right angles thereto. The spacers on each of the shellsare so separated that thestuds thereon may be inserted through thegrommets 38 in the trays 25, 26 respectively, `and are` retained inplace by nuts 44 screwed on the ends of the stud projecting from theouter end of the grommets.

By means` of such construction when the trays are juxtaposed asheretofore described, with the shells 2|, 22 positioned around thedielectric casing I3, the springV spacers 49 will be slightly com-Vpressed, resiliently urging the shells against said casing I3 which willbe encompassed by said shells.

In order that the shells 2|, 22 be electrically insulated vfrom thetrays 25, 2S, the length thereof isrslightly less than that of thesemi-cylindrical floors 28 in said trays, providing a gap 45, betweenthe ends of the shells and the associated end Walls 23', 3| of thetrays.

To provide for electrical continuity between the ends I B,` I9 of thesevered outer conductor l1, meansare provided to connect such ends tothe associated ends 'of'the conductive structure or' s formed'integrallywith the ends of each of the fifi trays respectively and extendingoutwardly therefrom. Each connector member has a semi-cylindricaltroughV 48` therein of diameter substantially the same as the diameterof the casing vI3. Troughs 43 are'coaxial with oor 28 of theassociatedftray' and are 'in'communication with said floor 234through 4asemi-circular notch 49 in each of theend walls 25 rand 3| which notches49"` have the same diameter as trough 48.

The troughs 4 3 in lthe connector member 46,

4l are sorposiftioned with respect'to the iioor` 28r of the associatedVtray that'when the trays are, juxtaposed, with the shells 2l, 22therein encompassing casing I3, theminner surfaces of the troughs 48inthe connector members, will be longitudinally alignedwith theinnersurface of" the shells, thereby ensuring that the dielectricy casing I3will'be resting-against the inner surfaces of troughs 48,"which form abore 59, and againstv the inner surfaces of shells 2|, 22.

Preferably each of theconnector members 46, 41 at its root end has asemi-cylindrical ledge 5| and the thickness of the connector member isgradually reduced from said ledge 5| to thenose end 52 thereof, taperingto substantially a knife edge thereat, with "the outerv diameter of saidknife edge 52 lbeing substantially the same as the inner diameter 'ofthe'outer conductor Il. To installnthe device: it is first necessary toprepare the coaxial cable I by removing a small section of the outercovering I6 thereof of length slightly greater than the overall lengthof the housing I2 including the connector members 45, 41. The exposedouter conductor I1 is severed in the mid portion thereof without cuttingthe dielectric casing I3 therebelow and each of the severed ends I8 andI9 of said outer conductor is pushed back as shown in Fig. 1. This willcause the braided outer conductor to flare out as at I1 so that it Willbe of greater diameter at its severed ends.

One of the trays, illustratively tray 26, with a, shell 22 mountedtherein as heretofore described, is thereupon positioned about thecoaxial cable so that the exposed dielectric casing I3 rests on theassociated shell 22 and in the troughs 48 in connector members 46, 41,with the knife edges 52 at the noses of such members 46, 41 extendingbetween the outer conductor I1 at the severed end thereof and thedielectric casing I3'. This procedure is repeated with the other tray25, the dowels 33 aligning such trays when they are juxtaposed.

The flared ends of the outer conductor I1 are thereupon pushed up on thejuxtaposed connector members which form a frusto-conical contour, untilthe ends I8, I9 of the outer conductor I1 are on the associated ledge5I. By means of any suitable clamp means 55 positioned around the rootends of the juxtaposed connector members, over the ends I8', I9 of theouter connector I1 and the ledge 5I, the ends I8, I9 may be securelyretained against their associated ledge 5I, the clamp also securelyretaining the juxtaposed trays 25, 26 together.

As the knife edges 52 of the connector members extend between the flaredportions I1' of the outer conductor I1 and the dielectric casing I3 tocontact the innei` surface of such Outer conductor as at 56 Where it hassubstantially its original diameter, and as the inner surface of theshells 2I and 22 are aligned with the inner surface of said troughs inthe connector members, it is apparent that for all practical purposes,the casing i3 will have an outer conductor therearound the distance ofwhich, from the inner conductor I4, will not be varied by theinterposition of said coupling unit. As the electrical continuity of theouter conductor is provided by the housing itself, and as the innerconductor I4 is not physically disturbed by the coupling device, the`gaps 45 between the shells 2I, 22 and the housing, will have negligibleeffect in producing an impedance discontinuity in the coaxial cable I5.

The coupling device itself essentially comprises a section of coaxialtransmission line interposed in the main line with the shells 2 I, 22forming the inner conductor and the wall of the cavity 32 forming theouter conductor. It is important that the characteristic impedance ofthe coupling device be substantially the same as that of the line toprevent impedance discontinuity.

As the diameter of each 0f the shells 2|, 22 is determined by thediameter of the casing I3 which they straddle it is only necessary todetermine the inner diameter of the floors 28 which, when juxtaposed,form the cylindrical cavity about the shells 2 I, 22. This may readilybe calculated from the formula Z0: 10g10 all Awhere Z0=characteristicimpedance of the line.

=inner diameter of the outer conductor and a=outer diameter of the innerconductor. Assuming the cable to have a characteristic impedance Z0 of52 ohms and the outer diameter a of the shells to be .34 inch, we findor b=2.4 .34=.82 inches, which is the required diameter of floors 28 sothat the coupling device will have a characteristic impedance of 52ohms.

A radio frequency receiver may be connected to the coupling device asshown in Fig. 3 by attaching one of the leads i. e. lead 60 from thereceiver 62, to the projecting end of a stud 43 on one of the shells andby connecting the other lead, i. e. lead 6I, to the housing I2. As theshells 2|, 22 are electrically insulated from each other, one of themmay be used to couple energy to one unit and the other to couple energyto another unit (not shown). As only a portion of the energy in thetransmission line I5 is generally required to actuate the receiver 62 aseries resistance R may be inserted in one of the feeder leads,illustratively lead 60 as shown in Fig. 4.

The following are typical calculations to determine the value of R atmegacycles which is illustratively chosen as the mid point of thefrequency range at which at receiver, such as a television set, is tooperate.

Where, for example, it is desired that voltage fed into the receiver 62be 30 decibels less than the voltage across the transmission line, theimpedance Zp looking into the feeder leads 60, 6I at the receiver towardthe coupling device should be approximately 31 times the characterisicimpedance Zo of the tranmission line itself.

Assuming the characteristic impedance Z0 of the transmission line to be52 ohms, its capacitance per foot is known to be approximately 29 mmf.Assuming the length of the pick-up shells to be two inches each, thenthe capacitance of the pick-up member will be or approximately 5 mmf.

At 100 mc., the capacitance reactance Xe of the pick-up member canreadily be ascertained by the formula 1 Zc-m when f=frequency inmegacycle and c=capaci tance in mmf., and is found t0 be approximately320 ohms.

Applying conventional formulas then and R is found to be approximately1530 ohms.

Since R is large as compared to XC, Zp will not vary appreciably overthe range of frequencies from 50 mc. to 200 mc. thereby assuring almostconstant signal voltage transfer to a television receiver at allfrequencies in this range.

If desired resistor R may be eliminated if the shells are constructed ofresistive material such as carbon or nichrome. The equivalent electricalcircuit will still be such that a resistor will appear in series withthe pick-up producing the required isolation.

With such coupling device, long runs of line may be used between thecoupling device and a receiver with no effect on the main transmissionline on which the coupling device is mounted and a short circuit betweentheshells 2i and 22 and the outer conductor Il or the housing', eitherin the device itself or external' to it'will not aiect the signalspassing hrough the ttrans'missionline I5 for such short circuit willmerely electrically restore the line to its original form and onlydisable the receiver connected tothe 'defective coupling device.

The number of receivers that may beA fed from a distribution lineutilizing the coupling 'device herein described is limited mainly by thelength of the line, as discontinuity losses in the 'line produced by thetapping in of suchreceivers is kept ata minimum.

Because the device is capacitive, more voltage will? be transferred tothe receivers at high frequencies than at low frequencies henceautomatically compensating for the greater losses in the line at suchhigher frequencies.

Asthe coupling unit maybe added to the line with but a few operationswithout-need for cutting the dielectric casing or inner conductor andWithout need for soldering-theaddition of such device is a relativelysimple procedure that does not require the services of a 'slrilled'radio'me'- chanic but may be performed by any electrician.

As many changes couldfbe made in the above construction, and many'apparently widely 'different embodiments of this invention could bemade without departing from the scope of the claims, it is intended thatall matter contained in the above description or shown'in theaccompanying drawings shall be interpretedas illustrative and not in alimiting sense.

`Having thus described my invention, what I claim as new and desireto'secure 'by Letters Patent of the United States is:

1. A device for transferring energy from along the length of a coaxialcable transmission line, said device comprising a capacitative pick-upmember adapted to encompass and extend longitudinally of the dielectriccasing of such .cable from which a portion of the outer covering hasbeen removed and the outer conductor severed to expose such dielectriccasing, means to retain said pick-up member against such dielectriccasing, a conductive structure having a portion thereof extendingparallel to said pick-upmember and spaced therefrom, said parallelextending portion and said pick-up memberbeing spaced so as to form asection of transmission line having the same characteristic impedance asthe coaxial cable to which the device -is aixed, and means to connectthe severed ends of such outer conductor to said structure.

2. The combination set forth in claim 1 in ywhich said pick-up membercomprises a plurai- :ity of substantially semi-'cylindrical shells ofcon- .riuctive material.

3. A device for transferring energy from along the length of a coaxialcable transmission line, said device comprising a capacitative pick-upmember' adapted to encompass and extend longitudinally of the dielectriccasing `of ,such cable from which a portion of the outer covering hasbeen removed and the outer conductor severed `to expose such dielectriccasing, and a conductive structure having a cylindrical cavity vvthereinencompassing said pic'x-up member and coaxial therewith, the wall ofsaid cavity and said pickup member being spaced so as to form 2, sectionof transmission line having the same characteristic impedance as thecoaxial cable to which the device is affixed, saidstructure having meansthereon for connection thereto of the severedlends QiihgouterQQnCluCtQr.- Y

'4. The combination set forth in claim 3 which vmeans are provided onsaid pick-up member coacting with said structure and insulated therefromsecurely to retain said pick-up mem ber against such dielectric casing.

5. A device for transferring energy from along the length of a coaxialcable transmission line, said device Comprising a capacitative,substantially cylindrical pick-up member adapted to encompass and extendlongitudinally of the dielectric casing of such cable from which aportion of the outer covering has been removed and the outer conductorsevered to expose such dielectric casing, said pick-up member having aninner diarneter substantially the same as that of such outer conductor,a housing of conductive material having a cylindrical cavity thereinencompassing sailrpiclg-up member and coaxial therewith, the wall of said cavity and said pick-up member being spaced so as to form a sectionof transmission line having the same characteristic impedance as thecoaxial cable to which the device is aflixed, means on said pick-upmember coacting with said housing and insulated therefrom securely toretain said pick-up member against such dielectric casing and means onsaid housing or connection thereto of the severed ends of the outerconductor.

6. The combination set forth in claim 5 in which said last named meanscomprises a pair of frusto-conical conductive members extendinglongitudinally outward from said housing at each end thereof and rigidtherewith, said members eachlhaving a bore therethrough 'coaxial withsaid cylindrical cavity and of diameter substantially equal to that ofsuch dielectric casing, which casing extends through said bore, wherebysaid fijnste-conical members may be positioned be@ tween the severedends of the outer conductor reg spectively and the dielectric casing,and 4clamp means are provided associated with each of said trusteconicalmembers respectively, to ax the sev-ered ends of such outer conductorthereto.

7. The combination set forth in claim 5 in which said last named meanscomprises a pair of truste-conical conductive members extendinglongitudinally outward from said housing at each end thereof and rigidtherewith, said members Qih having a bore therethrough coaxial with saidcylindrical cavity and of diameter substantially equal to that of suchdielectric casing, which casing extends through said bore, saidfrusto-conical members each having a ledge portion at the root endthereof and substantially a knife edge at the nose end thereof, wherebysaid frusto-conical members may be positioned between the severed endsof the outer conductor -respectively and the dielectric casing, Withsaid severed ends respectively resting on an associated ledge and clampmeans are `provided asso-.- cated with each of said frusto-conicalmembers respectively to alhx the severed ends of such outerconductorthereto, said knife edge of said frusto.- conical membershaving an outer diameter substantially the saine as the inner diameterof such outer conductor.

8. A device for transferring energy from along the-length of a coaxialVcable transmission line, said device comprising a capacitative,substantially cylindrical pick-up member adapted toencompass and extendlongitudinally of thev ydielectric casing of such cable from which aportion of the outer covering has 'been removed and the outer conductorsevered to expose such dielestricaiea Said pivkfupmember having ancurely to retain said inner diameter substantially the same as that of:such outer conductor, a housing of conductive material, means on saidpick-up member coacting with said housing and insulated therefromsepick-up member against such dielectric casing, said housing comprisinga pair of substantially identical trays each having a body portion witha longitudinal semi-cylindrical floor therein, which iloors when saidtrays are juxtaposed, form a substantially cylindrical cavityvencompassing said pick-up member and coaxial therewith, the wall ofsaid cavity and said pickup member being spaced so as to form a sectionof transmission line having the same characteristie impedance as thecoaxial cable to' which the device is affixed and means on said housingfor connection thereto of the severed ends of the outer conductor.

9. A device for transferring energy from along the length of a coaxialcable transmission line, said device comprising a capacitative,substantially cylindrical pick-up member adapted to encompass and extendlongitudinally of the dielectric casing of such, cable from which aportion of the outer covering has been removed and the outer conductorsevered to expose such dielectric casing, said pick-up member having aninner diameter substantially the same as that of such outer conductor, ahousing of conductive material, means on said pick-up member coactingwith said housing and insulated therefrom securely to retain saidpick-up member against such dielectric casing, said housing comprising apair of substantially identical trays, each having a body portion with alongitudinal semicylindrical floor therein, said floors having a greaterdiameter than said pick-up member, and a pair of substantially identicalconnector members of conductive material extending longitudinallyoutward from the tray at each end thereof respectively and rigidtherewith, said connector members each having a semi-cylindricallongitudinal trough therein in communication with the semi-cylindricalfloor in said body portion and coaxial therewith and of diametersubstantially equal to that of the dielectric casing, whereby when saidtrays are juxtaposed and positioned about said pick-up member, thesemicylindrical floors of the body portions will form a cylindricalcavity encompassing said pick-up member and the troughs in saidconnector members will form a bore through which the dielectric casingmay extend, the wall of said cavity and said pick-up member being spacedso as to form a section of transmission line having the samecharacteristic impedance as the coaxial cable to which the device isailixed and means coacting with the juxtaposed connector members toaillx the severed ends of such outer conductor thereto.

10. The combination set forth in claim 9 in which said connector memberseach have a ledge portion at their root ends and taper to substantiallya knife edge at their nose ends and the severed ends of such outerconductors are flared from the ends of the portions of such cable fromwhich the outer covering has been removed, whereby when said connectormembers are juxtaposed, associated pairs thereof may be positionedbetween the severed ends of the outer conductor respectively and thedielectric casing, with such severed ends resting on said ledgesrespectively and said knife edge nose extending to the ends of theportion of the cable from which the outer covering has been removed andin engagement with the inner Wall of such outer conductor and 10provided lcoacting with said securely to retain such severed -clampmeans areledges respectively, ends thereagainst.

l1. A device for transferring energy from along the length of a coaxialcable transmission line, said device comprising a capacitative pick-upmember including two substantially semi-cylindrical shells, each havinga radius of curvature substantially equal to that of the dielectriccasing of such cable from which a portion of the outer covering has beenremoved and the outer conductor severed to expose such dielectriccasing, a housing of conductive material having a cylindrical cavityvtherein, means on said shells coacting withsaidhousing and-insulatedtherefrom securelyto retain said shells against such dielectric casingextending longitudinally thereof with said cylindrical cavityencompassingsaid pick-up member and coaxial therewith, the wall of saidcavity and 'said pick-up member being spaced so as to form a section oftransmission line vhaving the same characteristic impedance as thecoaxial cable to which the device is affixed, and means on said housingfor connection thereto of the severed ends of the outer conductor.

12. A device for transferring energy from along .the length of a coaxialcable transmission line, said device comprising a capacitative pick-upmember including two substantially semi-cylindrical shells, each havinga radius of curvature substantially equal to that of the dielectriccasing of such cable from which a portion of the outer covering has beenremoved and the outer conductor severed to expose such dielectriccasing, a housing of conductive material, means on said shells coactingwith said housing and insulated therefrom securely to retain said shellsagainst such dielectric casing, said housing comprising a pair ofsubstantially identical trays each having a body portion with alongitudinal semicylindrical floor therein, said floors having a greaterdiameter than said pick-up member, which iloors when said trays arejuxtaposed form a substantially cylindrical cavity encompassing saidpick-up member and coaxial therewith, the Wall of said cavity and saidpick-up member being spaced so as to form a section of transmission linehaving the same characteristic impedance as the coaxial cable to whichthe device is affixed, and means on said housing for connection theretoof the severed ends of the outer conductor.

13. A device for transferring energy from along the length of a coaxialcable transmission line, said device comprising a capacitative pick-upmember including two substantially semi-cylindrical shells, each havinga radius of curvature substantially equal to that of the dielectriccasing of such cable from which a portion of the outer covering has beenremoved and the outer conductor severed to expose such dielectriccasing, a housing of conductive material, means on said shells coactingwith said housing and insulated therefrom securely to retain said shellsagainst such dielectric casing, said housing comprising a pair ofsubstantially identical trays, each having a body portion with alongitudinal semi-cylindrical iloor therein, said floors having agreater diameter than said pick-up member and a pair of substantiallyidentical connector members of conductive material extendinglongitudinally outward from the trays at each end thereof respectively,said connector members each having a semi-cylindrical longitudinaltrough therein in communication with the semi-cylindrical floor in saidbody portion and of diameter substantially 'equal to that oiItl'lefdielectricV casing,l whereby Awhen'/-said-traysare juxtaposedland positioned about said pick-up member, thef-semi-cylndrical"iioors'f in the body portionswll form a' cylindricalcavity'fencompassir'ig said` v pick-up member and the troughs in saidconnector 1members-wi1l form a bore through which the dielectric casingmay extend, the-Wall of said cavity and said pick-up memberfbeing spacedso as to 'form a section of transmission line havingy the A-sarnecharacteristic impedance'as the coaxial cable to .Which'the devvice isaflixed'and meanscoacti-ngwith the juxta- Y posed'connectormembersto'aflixthe-severed ends of such outer conductor thereto. 14; Thecombination set forth in= claim-13 'in which each ofv said shells isslightly'less than a usemicirclel -in cross 'section and the Ylongitudinal e'dgesoi` said shellsare spaced from each other whenretained against' suchdielectric casing.

'515'. The combination setforth in* claim 13 in Which'saidfshel-ls are`of highly resistivematerial, 16,1 4The combination set'iorth in claim13`in which-the means'on said shells to retain the latter Vhasibeenremoved and they Vouter conductor severedgto exposethe'dielectricicasing'in which the inner conductor is embedded, aicoupling. device comprisinga capactative pick-up member havingta'generallyv cylindrical shell encompassing such AVexposed dielectriccasing and spaced from said outerV conductor to form an electriccondenser-with'respectlto the inner conductor, and a; conductivestructure electrically connecting'the severedends ofsuch "outerconductor, extending parallel to v'said vshell and spaced therefrom "soas to' forma section Vof transmission line having substantially the samevcharacteristicimpedance as such coaxial cable; whereby when a radiofrelquencyreceiver isv connectedto vsaid conducting -structure'a-ndsai-dY shell, energywill be transferred'irom said-coaxial cabletosuchreceiver without any substantial impedance'discontnmity inf-said coaxialcable:

BENJAMIN ADLER.

REFERENCES CITED YThefiollovving references are of recordin the iile'ofthis patent:

UNITED STATES PATENTS Number Name Date 1,708,292 Buysv Apr. 9, 192921,092,647 Hobart Sept. '7, 1937 2,442,614 Norton June 1, 1948 2,451,868v.Quackenbush- Oct. '19, 1948

